Compound carburetion system



April 12, 1955 BRAUN 2,705,942

COMPOUND CARBURETION SYSTEM Filed June 27, 1952 lnnentor attorneys United States Patent COMPOUND CARBURETION SYSTEIVI Adolph F. Braun, Davison, Mich., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Original application July 28, 1949, Serial No. 107,277,

now Patent No. 2,647,502, dated August 4, 1953. Divided and this application June 27, 1952, Serial No. 295,860

9 Claims. (Cl. 123-127) This invention relates to compound carburetion systems for internal combustion engines, i. e., carbureton systems which include a plurality of carburetors which cornmunicate with the same cylinder or cylinders of the engine and are so controlled that when the engine is operating at lower speeds combustible mixture is supplied to the cylinder or cylinders by only one of the carburetors and when the engine is operating at higher speeds combustible mixture is supplied to the cylinder or cylinders by a plurality of the carburetors.

The invention resides in improvements in the compound carburetion system disclosed in my United States Patent No. 2,434,192, dated January 6, 1948, by which the secondary carburetor or carburetors are brought into operation with the minimum departure from the desired rate of acceleration of the speed of the engine, which minimize the discrepancies between the volumes of combustible mixture supplied to the several cylinders of a multi-cylinder engine, and which minimize the height of and render the carbureting apparatus more compact.

Also this application is a division of my co-pending ap plication for patent Serial Number 107,277, filed July 28, 1949, for Compound Carburetion System, now Patent Number 2,647,502, issued August 4, 1953.

For a better understanding of the objects and nature of this invention, reference is made to the following specification and the accompanying drawing, wherein embodiments of the invention are described and illustrated.

In the accompanying drawing:

Figure 1 is a fragmentary side elevation of a multicylinder internal combustion engine equipped with carbureting apparatus in which my invention is embodied.

Figure 2 is an enlarged side elevation, with parts broken away and in section, of the secondary carburetor of the carbureting apparatus shown in Figure 1.

Figure 3 is a side elevation, with parts broken away and in section, of another embodiment of my invention.

In the drawing, the reference character indicates a multi-cylinder internal combustion engine with an intake manifold 11 which communicates with a plurality of the cylinders of the engine. On the intake manifold, forward of its midpoint, there is disposed a primary carburetor 12 and, to the rear of its midpoint, a secondary carburetor 13. The primary carburetor may be of the conventional type with a mixture passage 14 in which there is disposed a butterfly throttle valve 15 mounted on a shaft 16 to which there is fixed an arm 17. The arm 17 is connected by a link 18 to a lever 19 mounted so that it may rock on a shaft 20 and to which there is also connected a link 21 through which the lever 19 may be rocked by the accelerator pedal of the vehicle. To an arm 22 on the lever 19 there is connected a spring 23 which biases the throttle valve 15 to its closed position.

The secondary carburetor 13 includes a mixture passage 24 in which there is disposed a butterfly throttle valve 25 which is mounted on a shaft 26. On the shaft 26 there is mounted so that it may rock an arm 27. To the shaft 26 there is fixed a double-armed lever 28 with a pin 29 on one of its arms in the path of the arm 27 when the latter is moved in the direction to close the throttle valve 25. The arm 27 is connected by a link 30 to a lever 31 which is mounted so that it may rock on the shaft 20 in the path of the lever 19 when the latter is rocked to open the throttle valve 15. The lever 31 is biased by a spring 32 in the direction to move the arm 27 on the shaft of the throttle valve 25 of the secondary carburetor in the direction to close the throttle valve.

On the secondary carburetor 13 there is mounted a pressure responsive device which consists of an enclosure 33 with a flexible wall 34 which is connected by a link 35 to the arm of the lever 28 which does not carry the pin 29 and is biased by a spring 36 in the direction to close the throttle valve. The interior of the enclosure 33 is connected to the mixture passage of the secondary carburetor on the engine side of the throttle valve by a duct which includes a tube 37 and a bore 38 with a valve housing 39 interposed between them. In the valve housing 39, there is disposed a piston valve 40 which is biased by a spring 41 to a position in which the tube 37 communicates with the bore 38 through the valve housing 39 but is movable by suction in the manifold 11 to a position in which it interrupts communication between the bore and the tube.

The lever 19, of course, does not come into contact with the lever 31 until the throttle valve 15 of the primary carburetor has been opened to a pre-selected extent, e. g., about one half. Consequently, until the throttle valve of the primary carburetor has been opened to this extent the throttle valve 25 of the secondary carburetor is held closed by the spring 32.

However, after the throttle valve of the primary carburetor has been opened to the pre-selected extent, further movement of the accelerator pedal in the direction to open the throttle valve of the primary carburetor will ring the lever 19 into contact with the lever 31 and, thereafter, move the latter with the former. This movement of the lever 31 will, through the link 30, move the arm 27 on the shaft of the throttle valve of the secondary carburetor out of contact with the pin 29 on the doublearmed lever 28. The piston valve 40 is moved by the suction in the intake manifold 11 to a position in which it interrupts communication between the bore 38 and the tube 37 only when the suction attains the high values it attains when the throttle valves are closed or nearly closed and serves to eliminate the tendency which the suction acting through the diaphragm 34 would otherwise have to open the throttle valve of the secondary carburetor under this condition. Consequently, when the throttle valve of the primary carburetor has been opened sufficiently to move the arm 27 out of contact with the pin 29 the suction in the intake manifold will be applied to the diaphragm 34 and if the suction is sufificiently high will open the throttle valve of the secondary carburetor to the limit permitted by the arm 27. Therefore, after the throttle valve of the primary carburetor has been opened sufiiciently to move the arm 27 out of contact with the pin 29 the position of the throttle valve of the secondary carburetor will depend upon the value of the suction in the intake manifold as well as upon the position of the throttle valve of the primary carburetor as is desirable in the interest of satisfactory operation of the engine under difierent loads. The movement of the arm 27 is so correlated with the movement of the throttle valve of the primary carburetor that the former reaches the position in which it permits the throttle valve of the secondary carburetor to be opened wide when the latter reaches its wide open position.

In the modification of the invention shown in Figure 3 of the drawing, the primary and secondary carburetors are juxtaposed and made in a single unit which is mounted on the intake manifold 11 of the engine midway between its ends. In the mixture passage of the primary carburetor there is disposed a butterfly throtttle valve 51 which is mounted on a shaft 52 to which is fixed an arm 53 which is connected by a link 67 to the accelerator pedal of the vehicle and on which is formed a cam 54.

In the mixture passage 55 of the secondary carburetor, there is disposed a butterfly throttle valve 56 which is mounted on a shaft 57. To the shaft 57 there is fixed an arm 58 with a pin 59 on it in the path of the cam 54 on the arm 53 when the latter is moved in the direction to close the throttle valve 51. On the shaft 57 there is mounted so that it may rock a double-armed lever 60 with a pin 61 on one of its arms in the path of the arm 58 when it is moved in the direction to close the throttle valve 56.

On the secondary carburetor, there is mounted a pressure responsive device which consists of an enclosure 62 with a flexible wall 63 which is connected by a link 6ft to the arm of the lever 60 which does not carry the pm 61 and is biased by a spring 65 in the direction to close the throttle valve 56. The interior of the enclosure 62 is connected by a tube 66 to the mixture passage 50 of the primary carburetor on the atmospheric side of the throttle valve 51.

The cam 54 on the arm 53 on the shaft 52 of the throttle valve 51 of the primary carburetor is so shaped that it holds the throttle valve 56 of the secondary carburetor closed when the primary throttle valve 51 is closed. It may also be considered desirable to form the surface of the cam 54 in such manner that it will hold the secondary throttle valve 56 in closed position until the throttle valve of the primary carburetor has been opened to a predetermined extent or about one-half. Thereafter, the form of cam 54 may permit the throttle valve of the secondary carburetor to open gradually as the throttle valve of the primary carburetor is opened and to be opened to the greatest possible extent, or fully opened when the throttle valve of the primary carburetor reaches its wide open position. The connection of the tube 66 to the mixture passage of the primary carburetor on the atmospheric rather than the engine side of the throttle valve 51 obviates a valve like the valve 40 in the embodiment of the invention shown in Figures 1 and 2 in the duct which connects the interior of the enclosure 62 to the mixture passage. The embodiment of the invention shown in Fi ure 3 operates similarly to the embodiment shown in Figures 1 and 2 and it is thought that its operation will be understood without further explanation.

It will be apparent that when the engine is started the flow of air through the primary mixture passage 50 will cause a ess than atm spheric pressure to be im osed on the diaphragm 63 which will tend to compress the spring 65 to move the lever 60 so that the pin 61 may engage the edge of the lever 58. Due to the position of the lever 58 u on the shaft 57 it will be apparent that the weight of the lever 58 will tend to move the secondary throttle 56 toward closed position. The wei ht of the lever 58 will also tend to move the lever 58 toward the pin 61. As the primary throttle 51 is opened, it will be apparent that the cam surface 54 will move with respect to the pin 59 on the lever 58 until the throttle 51 is in fully opened position as is shown in broken lines in Figure 3. However, the pin 59 may or may not follow the surface of the cam 54, this being dependent on whether the opening of the throttle 51 increases the speed of the engine enough to reduce the pressure on the diaphragm 63 and to overcome the spring 65 so that the lever 60 will be moved to cause the pin 61 to engage and to move the lever 58 into a position in which the pin 59 engages the surface 54. In any event and regardless of the extent of the reduction in pressure on the diaphragm 63 the secondary throttle 56 cannot open beyond the position established by engagement between the pin 59 and the cam surface 58 as is shown in the dot and dash line position of the valves 51 and 56. The cam surface 54 is formed to limit the opening movement of the secondary throttle 56 to a position in which the valve 56 is aligned with the axis of the secondary mixture passage 55. In other words. when the primary throttle 51 is moved from closed to fully open positions the secondary throttle will be prevented by the cam 54 from moving farther than from closed to fully open positions. However, whether the secondary throttle 56 does move from closed to fully open positions depends on the response of the engine to the opening movement of the primary throttle 51. If the load on the engine is great the flow of air in the primary passage 50 may not increase to the extent requi ed to impose a suction on the diaphragm 63 which is sufficient to overcome the spring 65 and to cause the pin 59 to follow the cam surface 54. However, when the speed of the engine does increase to the desired extent, then the increase in the flow of air in the primary mixture passage 50 will cause a reduction in pressure on the diaphragm 63 which will overcome the spring 55 to move the pin 59 into engagement with the cam surface 54. When the primary throttle 51 is fully open and the engine speed is sufiiciently increased, then the suction affecting the diaphragm 63 will move the pin 59 against the end of the cam surface 54 to fully open the secondary throttle 56. However, it will be apparent from the dotted line positions of the valves 51 and 56 in the fully open positions of the valves, that the end of the cam surface 54 will limit the movement of the secondary throttle 56 so that the secondary throttle cannot be moved beyond the fully open position.

It will be apparent that the fixed stop linkage means represented by the throttle levers 53 and 58 and the cam 54 and pin 59 represent a positive control mechanism which may be constructed in any suitable manner to provide any desired relation between the opening movement of the primary throttle and secondary throttles 51 and 56 respectively. However, regardless of the contour of the cam 54 the linkage mechanism may be made in such manner that the secondary throttle will not open until the speed of the engine is increased to the desired extent. It will be apparent that the extent of the possible opening of the secondary throttle with respect to the primary throttle does not depend on engine suction but upon the contour of the cam 54 which in any position of the primary throttle 51 will act as a positive stop to limit the opening of the secondary throttle per degree of opening movement of the primary throttle to the amount determined by the contour of the cam 54. It will be further apparent that the cam 54 may be made to give any desired series of limits to the opening of the secondary throttle per degree of opening movement of the primary throttle.

By the provision of the secondary carburetors and the correlation of the movement of their throttle valves with the movement of the throttle valves of the primary carburetors in the manners which have been illustrated and described, my invention insures satisfactory operation of the engine at relatively low speeds without sacrificing anything in the matter of operation of the engine at higher speeds. The throttle valves of the secondary as well as the primary carburetors are preferably balanced so that, per se, they are unaffected by the suction in the intake manifold. The provision of the throttle valves of this type in the secondary carburetors actuated by pressure responsive devices tends to bring the secondary carburetors into operation with the minimum departure from the desired rate of acceleration of the speed of the engine and the provision in the secondary carburetors of throttle valves of this type whose opening movement is limited in accordance with the position of the throttle valves of the primary carburetors obviates manually operated throttle valves in the secondary carburetors and thus minimizes the height of and renders the carburetors more compact. Disposition of the carburetors midway between ends of the manifold as in the embodiment of the invention shown in Figure 3 minimizes the discrepancies between the volumes of combustible mixture supplied to the several cylinders of the engine.

I claim:

1. A compound carburetion system for an internal combustion engine having a cylinder and comprising primary and secondary inlet passages for supplying combustible mixtures to said cylinder and having primary and secondary throttles respectively in said passages, pressure responsive means associated with said system for operating said secondary throttle in response to the flow of mixture in one of said inlet passages, operating means including a link associated with said secondary throttle and connected to said pressure responsive means for opening and closing said secondary throttle under certain conditions of operation of said engine, a conduit between said pressure responsive means and one of said inlet passages and establishing in said pressure responsive means the fluid pressure resulting from the flow of mixture in said one of said inlet passages, and fixed stop linkage means between said primary throttle and said secondary throttle and operable between the closed and fully opened positions of said throttles to limit the possible opening of said secondary throttle by said pressure responsive means at each position of said primary throttle, said stop linkage means including an operating arm fixed to the secondary throttle shaft exteriorly of said inlet passages, a member proximate said arm and adapted to coact therewith to variably limit the movement of said secondary throttle in the opening direction, said member being operatively connected to the primary throttle so that the degree of opening of the secondary throttle cannot exceed that of the primary throttle, said operating means and said fixed stop linkage means being formed to provide a lost motion connection between said pressure responsive means and said secondary throttle and providing for the full opening of said primary throttle without any opening of said secondary throttle.

2. A compound carburetion system for an internal combustion engine having a cylinder and comprising primary and secondary inlet passages for supplying combustible mixtures to said cylinder and having primary and secondary throttles respectively in said passages, pressure responsive means associated with said system for operating said secondary throttle in response to the flow of mixture in said primary inlet passage, operating means including a link associated with said secondary throttle and connected to said pressure responsive means for opening and closing said secondary throttle under certain conditions of operation of said engine, a conduit between said pressure responsive means and said primary inlet passage on the atmosphere side of said primary throttle and establishing in said pressure responsive device and throughout all operating conditions of the engine the fluid pressure resulting from the flow of mixture in said primary passage and beyond said primary throttle, and fixed stop linkage means between said primary throttle and said secondary throttle and operable between the closed and fully open positions of said primary throttle and said secondary throttle and limiting the possible opening of said secondary throttle by said pressure responsive means at each position of said primary throttle, said stop linkage means including an operating arm fixed to the secondary throttle shaft exteriorly of said inlet passages, a member proximate said arm and adapted to coact therewith to variably limit the movement of said secondary throttle in the opening direction, said member being operatively connected to the primary throttle so that the degree of opening of the secondary throttle cannot exceed that of the primary throttle, said operating means and said fixed stop linkage means being formed to provide a lost motion connection between said pressure responsive means and said secondary throttle and providing for the full opening of said primary throttle without any opening of said secondary throttle, said fixed stop linkage means being formed to establish a predetermined relation between the opening of said primary throttle and the possible opening of said secondary throttle and to permit the continuous movement of said secondary throttle by said pressure responsive means and between said closed and said fully open positions and during the movement of said primary throttle between said closed and said fully open positions.

3. A compound carburetion system as defined by claim 1 and in which said conduit between said pressure responsive means and one of said inlet passages is connected to said secondary inlet passage between said secondary throttle and said cylinder and is controlled by a suction actuated valve tending to close said conduit when the fluid pressure in said secondary inlet passage is high and to open said conduit as the suction in said secondary inlet passage decreases.

4. A compound carburetion system as defined by claim 2 and in which said primary and secondary throttles are rotatably mounted on adjacent and parallel shafts adapted to rotate in opposite directions for closing or opening said primary and said secondary throttles and in which said fixed stop linkage means is associated with and mounted upon adjacent ends of said shafts.

5. In an internal combustion engine which includes a cylinder, a primary carburetor through which a combustible mixture may be supplied to the cylinder, a throttle valve in the primary carburetor, means for opening the throttle valve of the primary carburetor to a predetermined extent, a secondary carburetor through which a combustible mixture may be supplied to the cylinder, a throttle valve in the secondary carburetor, a pressure responsive device to which suction of the engine on the engine side of the throttle valves is communicated for opening the throttle valve of the secondary carburetor, means to interrupt communication of the suction of the engine to the suction actuated device when the suction of the engine on the engine side of the throttle valves is relatively high, and means which renders the effectiveness of the suction actuated device to open the thottle valve of the secondary carburetor dependent upon the opening of the throttle valve of the primary carburetor beyond said predetermined extent.

6. The internal combustion engine claimed in claim 5 in which the last-specified means is a valve to which the suction of the engine on the engine side of the throttle valves is communicated.

7. In an internal combustion engine which includes a cylinder, a primary carburetor through which a combustible mixture may be supplied to the cylinder, a throttle valve in the primary carburetor, means for opening the throttle valve of the primary carburetor, a secondary carburetor through which a combustible mixture may be supplied to the cylinder, a throttle valve in the secondary carburetor, a pressure responsive device to which suction of the engine on the atmospheric side of the throttle valve of the primary carburetor is communicated for opening the throttle valve of the secondary carburetor, and means which renders the effectiveness of the suction actuated device to open the throttle valve of the secondary carburetor dependent upon the movement of the throttle valve of the primary carburetor beyond an initial normal operating range for said primary carburetor.

8. A compound carburetion system for an internal combustion engine including primary and secondary inlet passages for supplying combustible mixture to the engine, primary and secondary throttles in said passages, a pressure responsive device for opening the secondary throttle, operating means for said pressure responsive device including a passage applying engine suction on the atmosphere side of the primary throttle to said device to open the secondary throttle, operating means for said primary throttle, and a member movable with the secondary throttle and having a lost motion connection with the primary throttle operating means to provide for the opening of the primary throttle without opening the secondary throttle and limiting the opening of the secondary throttle at each position of the primary throttle to an amount which has a fixed relation to the opening of the primary throttle under all operating conditions of the engme.

9. A compound carburetion system for an internal combustion engine as defined by claim 8 and in which said member having a lost motion connection with the primary throttle operating means provides for the full opening of the primary throttle without opening the secondary throttle and in which said secondary throttle is a balanced throttle that may be fully closed when the primary throttle commences to open.

References Cited in the file of this patent UNITED STATES PATENTS 2,317,625 Mallory Apr. 27, 1943 2,376,732 Strebinger May 22, 1945 2,460,046 Vincent Jan. 25, 1949 

